Additive compositions based on zinc dihydrocarbyl dithiophosphates have been extensively used in the past. However the performance capabilities of prior low ash additive compositions based on zinc dihydrocarbyl dithiophosphates can vary to a considerable extent.
A need has arisen for a low ash antiwear additive composition which exhibits high thermal and oxidative stability even when used at very low treat levels in lubricating oil base stocks. This invention is deemed to fulfill this need in an effective and economical manner.